1. Field of the Invention
The present invention relates to an electric bending endoscope apparatus having an electric bending endoscope which electrically bends a bending portion in a status corresponding to an absolute-position signal by operating bending operation instructing means for outputting the absolute-position signal.
2. Description of the Related Art
Recently, an endoscope is widely used for various curing treatments which are performed by inserting an elongated inserting portion in the celom so as to observe the organ in the celom or by using a treatment tool inserted in a treatment tool channel as needed.
The endoscope generally has a bending portion which is bent vertically or horizontally on a distal portion side. The bending portion is bent in a desired direction by stretching and contracting a bending wire connected to the bending portion.
In general, the bending wire is manually operated. However, the endoscope recently includes an electric bending endoscope which is stretched by bending motive means such as an electric motor. In the electric bending endoscope, the electric motor is rotated by a joystick for outputting a bending instructing signal of an absolute position, such as bending operation instructing means arranged to an operating portion. Then, the rotation of the electric motor rotates a pulley, the bending wire connected to the pulley is stretched, and the bending portion is bent.
The joystick instructs a bending position by being inclined. That is, a direction for inclining the joystick is one for bending the bending portion and an inclining angle of the joystick corresponds to a bending angle of the bending portion. When the inclining angle of the joystick is 0° as a straight status, the bending portion is in a non-bending status (straight status). Therefore, an operator can easily grasp a bending status of the bending portion in the celom with his sense of the finger which grips the joystick.
Namely, in the above-mentioned electric bending endoscope, the bending portion is easily and desirably bent by the single finger. Accordingly, the operability is improved because another finger operates other switches arranged to the operating portion. However, in the electric bending endoscope, the bending wire is always under tension irrespective of in the bending status or non-bending status. Then, the following is requested to the electric bending endoscope.
(1) Since the bending wire has a tendency to stretch by the tension, the stretch of the bending wire is prevented.
(2) The bending wire is not under the tension during manual inserting operation, and the bending portion is in a freely bending status by external force.
(3) When a default is caused during the inserting operation, the inserting portion is removed in the freely bending status.
Endoscopes to respond to the above requests are proposed. For example, an electric bending endoscope has means for restoring transmission and disconnection of driving force which can switch a status for disconnecting the transmission of driving force/a status for restoring the transmission of the driving force of the tension acting on the bending wire in accordance with the necessity. Further, Japanese Unexamined Patent Application Publication No. 6-269398 discloses an endoscope which surely switches a locking status and a free status of the bending portion by arranging status switching means which can switch a stretching status and a contracting status of a stretching member.